Critical Chain

From “Theory of Constraints” Developed by Elihu Goldratt in 1984

Goldratt – Many of his key ideas were first explained via “business novels” like The Goal: A Process of Ongoing Improvement.

What is the “Theory of Constraints”?

• The theory of constraints (TOC) is a management paradigm that views any manageable system as being limited in achieving more of its goals by a very small number of constraints.

• Based on “how people really behave.”• Includes lots of ideas to turn that into project

productivity!• “Critical chain” is one of these ideas…

The worst thing you can do for your process is try to make every step complete on time.

How long does it take you to get home for Thanksgiving?

How much safety do our estimates contain?

What causes Parkinson’s Law?

• Parkinson’s Law: Work expands to fill the time available

• Benefits of finishing early• Student syndrome• Multitasking

“And if you finish memorizing the names of all the presidents, go ahead and memorize the names of all the vice-presidents.”

Multitasking’s effects

What can we do?

Goldratt’s solution – Reduce the estimate of everything by half

(approximately) and move the buffer to the end

Why is this better?

1. Encourages folks to finish early2. Makes problems more visible3. Focuses attention on the real goal of the process

“Project buffer”

What about situations where there are complex dependencies?

B 6 D 10 F 5

E 3 G 5

H 10

A 8 C 5

“Project buffer”

“Feeding buffer”

Student syndrome & large projects

• Student syndrome: tendency of people to waste “safety buffer” without starting tasks – reintroducing risk no matter how generous the buffer

• A real problem on student projects with interdependencies

• You’ve seen how critical chain handles this problem

• Can we solve this problem at Rose?

Please don’t confuse critical path and critical chain

• Critical path is the longest path through a PERT chart

• Critical chain is this thing, with reduced estimation time and buffers– Within the overall methodology, there is also a

smaller thing called “critical chain” involving a critical path that takes into account certain resource contentions. Don’t worry about it.

Interesting issues with “student syndrome” here at Rose:

• Students work in a multi-assignment environment. It may even be true that "trying to balance the workload of all project resources is far too complex." Therefore, something like critical chain still may not work in the student context because balancing activities, sports, and other assignments.

• It may solve the "student syndrome" , but it may not work for students. It is really common that if a professor has a "buffer" (a professor is easy on their deadline), student will take advantages of it and keep pushing and missing deadline.

• It may not work because deadlines are put in place so that the student can complete the assignment before moving on to the next chunk of material to learn. If you did implement the chain process students would feel rushed to learn the material and complete the assignment in unrealistic time periods leading to confusion on the material they are learning.